In the realm of scanner, the scaling function is usually utilized. For instance, when a scanner having a resolution of 1200 dots per inch (dpi) is used to scan a picture having a resolution of 400 dpi, the scaling factor thereof is ⅓. Mutual coordination in the horizontal and vertical directions is required for the above scaling. If the scaling factor is ⅓, the scaling in the horizontal direction needs to be ⅓, and the scaling in the vertical direction also needs to be ⅓.
There are two kinds of manufacturing methods for the scaling in the horizontal direction, one being pixel-abstraction method, the other being pixel-average method. In the pixel-abstraction method, when a scanner scans a horizontal line, only one pixel is taken out from adjacent pixels to represent these n pixels. This method has the disadvantages of discontinuity and inferior image quality. In the pixel-average method, when a scanner scans a horizontal line, the average value of n adjacent pixels is used to represent these n pixels. This method can obtain better image quality, and has no disadvantage of discontinuity. Therefore, the pixel-average method is usually used as the manufacturing method for the scaling in the horizontal direction.
The commonly used scaling factors in the horizontal direction of a scanner are ⅔, ½, ⅓, ¼, ⅙, ⅛, 1/12, and so on. The above scaling factors are all combinations of 2, ½ and ⅓. That is, their functions can be achieved using combinations of (2, ½, ⅓). For instance, when the scaling factor is ⅙, ½ can first be done, and then ⅓; or ⅓ can first be done, and then ½.
During the average process, 2 or ½ can easily be achieved by left-shifting 1 bit (2) or right-shifting 1 bit (½) the added result of pixels. However, the manufacturing of ⅓ is much more difficult. There are two commonly used methods. One is dividing the added result of pixels by 3 using a divider. This method has the disadvantages of occupying a too large area (mainly because the divider occupies a too large area) and a too slow scanning speed due to a slower processing speed of the divider.
The other commonly used method is achieving the function of dividing by 3 through referring to a table. Although this method has a faster processing speed, a read only memory (ROM) thereof will occupy a very large area. With a 16-bit scanner as an example, there will be 16×216 decoders and 16×216 encoders. The more the number of bits, the faster the area increases. Therefore, this method also has the disadvantage of occupying a too large area.
Accordingly, the present invention aims to propose a device applied to scaling factor of horizontal scan of a scanner and a method thereof, whereby a simpler method can be used to manufacture scaling factor of horizontal scan of a scanner, and the area occupied by the device can be effectively decreased.